阳离子聚合物修饰纳米Pt颗粒的合成

Synthesis of Cationic Ionomer Modified Pt Nano-particles

以PDDA(聚二烯丙基二甲基氯化铵 )为修饰离子 ,采用化学还原法合成了季铵阳离子修饰的纳米Pt颗粒。结果表明 ,对于n(PDDA ,Mw～ 5 0 0 0 )∶n(Pt)为 10∶1、pH值为 8 5的反应体系 ,5min是较好的反应时间 ,此时合成的Pt颗粒的粒径为～ 4 5nm ,分散性良好。还原速度随PDDA含量的降低、pH值的增加而加快 ;采用不同聚合度的PDDA对Pt进行修饰时 ,由于随PDDA聚合度的增加 ,其位阻效应增强、静电效应减弱 ,因此 ,合成稳定的Pt颗粒体系所需的PDDA用量随PDDA聚合度的增加呈现先升后降的趋势。

Cationic ionomer modified Pt nano-particles were synthesized by chemical reduction using polydiallyldimethylammonium chloride(PDDA) as a modification ion. From a reaction solution containing a mixture of PDDA(M w=5 000) and Pt with n(PDDA)∶n(Pt)=10∶1 and pH value of 8.5, Pt nano-particles sized in ～4.5 nm were obtained in 5 min reaction. The reduction reaction rate increased with the decrease of the PDDA content and the increase of the pH. The steric hinderance effect of the modifier becomes greater and the electrostatic effect of the modifier reduces as a result of the increase in the degree of polymerization of PDDA. Therefore, the content of PDDA necessary for obtaining stable Pt particles first increases and then decreases as polymerization degree of PDDA increases.